Bluetooth: Classic: SMP: Recovery flag SMP_FLAG_BR_CONNECTED

The flag `SMP_FLAG_BR_CONNECTED` is cleared by the function
`smp_br_reset()` and `smp_br_init`. But the flag
`SMP_FLAG_BR_CONNECTED` should not be cleared at this time.

Recovery the flag `SMP_FLAG_BR_CONNECTED` after the all flags of SMP
cleared.

Signed-off-by: Lyle Zhu <lyle.zhu@nxp.com>